Chromatograph sample system



Nov. 4, 1969 c. R. FERRIN 3,475,950

CHROMATOGRAPH SAMPLE SYSTEM Filed Feb. 14. 1966 2 Sheets-Sheet 1 SOURCECARR/E SOURCE OF COLUM T0 CHROMATOGR I7 I To saunas 0F CHROMATOGRAPHEJECTING COLUMN DISCHARGE OF SAMPLE INVENTOR.

f fl 2- CHARLES R. FERRIN ATTORNEY Nov.'4, 1969 c. R. FERRIN 3,475,950

CHROMATOGRAPH SAMPLE SYSTEM Filed Feb. 14, 1966 2 Sheets-Sheet 2 SOURCEOF A EJECT/NG COLUMN SOURCE OF SOURCE OF ggr SEALING GAS.

7'0 SOURCE OF CHROMATOGRAPH EJECT/NG COLUMN 645 I- .n :R l 0 39A 36B 1 lI INVENTOR.

QHARLES R. FERRIN ATTORNEY United States Patent US. U. 73-23.]l 2 ClaimsABSTRAQT OF THE DISCLUSURE The movable element of a valve has a passagein which a high pressure liquid sample is inserted and transferred to achromatographic column. A source of sealing fluid is connected to thevalve to apply the high pressure fluid to the sealing surface about thevalve passage to prevent leakage of the sample.

The present invention relates to a method and apparatus of inserting asample of high pressure liquid into a chromatograph column. Moreparticularly, the invention relates to providing a pressure system for asample transfer valve which will effectively control a liquid sampletransferred by the valve from a source of sample to a chromatographcolumn.

One of the difficult problems in the art of chromatography is thetransfer of a prepared sample of high pressure liquid into achromatograph column. The nature of the chromatograph columns make itnecessary to supply small volumes of high pressure liquid samples. It isextremely diflicult to effectively isolate small sample volumes of highpressure liquid with mechanical valving structures and transfer thissample of liquid into a stream of carrier gas for entry into the column.The mechanical elements of valving structure are subject to wear withthe development of subsequent leaks.

The principal object of the present invention is to apply suflicientfluid pressure across the sealing surface of a valve element which isabout the ends of a sample-containing passage in the valve element whilethe transfer of the sample to connection with a chromatograph column isbeing made.

Another object is to provide for ejection of the high pressure liquidsample from the valve passage without interruption of the flow of thissample from the passage into the chromatograph column.

The present invention contemplates providing a plug valve fortransferring a high pressure liquid sample. A valve passage in the plugis supplied the sample of high pressure liquid for chromatographanalysis. While the sample is held in the plug passage, a separatesource of pressure is maintained on the sealing surface of the plug; thepressure being at least equal to that of the sample to thereby militateagainst leakage of the sample from the passage. The pressure on thesealing surface is maintained while the plug is positioned to connectthe plug passage to the column.

The invention further contemplates a source of fluid for ejecting thesample from the plug passage. The source of ejection fluid is sized soit will eject the sample from the plug passage without interruption ofits continuous flow into the column.

Having generally described the invention, it will now be explained inmore detail by reference to the accompanying drawings showing preferredembodiments of it and in which;

FIG. 1 is a partially sectioned side elevation of a high pressure liquidentrance system for a chromatograph in which the present invention isembodied;

3,475,950 Patented Nov. 4, 1969 "ice 2 12G. 2 is a sectioned plan viewof FIG. 1 along lines FIG. 3 is a view similar to FIG. 2 but with theplug of the valve positioned to eject the liquid sample into the column;and

FIG. 4 is a view similar to FIG. 1 but with a valve plug arranged withan internal passage to develop the balancing pressure on the plug.

The broad scope of the invention The problem is one of obtaining a verysmall volume of high pressure liquid and ejecting it into a stream ofcarrier gas for conveyance into, and through, a chromatograph column. Asmall passage can be formed in a valve plug for the liquid sample. Thesample can be trapped in this volume. However, in present practice, asthe plug is positioned, the slightest wear, or imperfection, results inan escape of some part of the liquid sample. The difference in pressurebetween that of the sample in the plug passage and ambient pressure onthe other side of the sealing surface has been great enough to permitthe escape of some of the sample. The chromatograph analysis has,heretofore, been inconsistent and inaccurate under these circumstances.

The present invention simply eliminates the pressure differential. Afluid pressure is generated on the sealing surface surrounding the plugpassage to reduce its pressure differential with the sample until noleakage of the sample takes place. This pressure is maintained on thevalve plug while it is positioned and no sample can escape.

The general system embodying the invention FIGS. l-3 illustrate oneembodiment of the invention in a system including a valve 1 with itshousing 2 connected to the necessary sources of fluids to be passed intoa chromatograph column for analysis. Plug 3 of the valve has a passage 4which receives the sample of high pressure liquid to be analyzed. Thesealing surface 5 of plug 3 extends about the ends of passage 4, sealingagainst the walls of housing cavity 6.

Housing cavity 6 has a volume 6A on one side of plug sealing surface 5and volume 6B on the other side of the plug sealing surface. Source 7simultaneously develops a fluid pressure in housing volumes 6A and 63great enough to retain the fluid sample in plug passage 4, eifectivelyisolated. The plug can then be rotated to the position disclosed in FIG.3 and the sample properly ejected from passage 4 and into the column.

Under this concept, the sealing of the high pressure liquid sample isnot solely dependent upon the effectiveness of the mechanical sealbetween the walls of plug 4 and the walls of housing cavity 6. Thepressure applied to each end of plug 3 accomplishes what mechanicalsealing has :failed to do in this art.

Details of FIGS. 1-3

Plug valves are well-known devices. The employment of Teflon plastic asthe movable element of such valves is also well-known. Theself-lubricating qualities of this material are generally understood andappreciated. Plug 3 is shown here as mounted on the end of a metallicbase 10 and turned by shaft 11 while spring-urged with spring 12 intosealing engagement with the walls of cavity 6. These parts are precisionmade in order to maintain alignment between plug passage 4 and passagesthrough the walls of housing 2.

FIGS. 2 and 3 show plug passage 4 rotated from the position at which itis filled with a sample to a position at which that sample is ejectedfrom passage 4 and into a chromatograph column. The sample source is notshown. It is only required for conduit 13 be disclosed, conducting thesample to housing passage 14. From passage 14, the

high pressure sample flows into plug passage 4. In actual practice, astream of the sample liquid is flowed through passage 4, housing passage15 and is discharged through conduit 16. When experience dictates thesample flowing through plug passage 4 is representative of the liquid tobe tested, plug 3 is rotated to connect plug passage 4 as shown in FIG.3. Gas from source 17 then ejects the liquid sample from plug passage 4and into conduit 18 for entrance into the chromatograph column notshown.

A source of carrier gas is indicated at 19. This source is connected tohousing passage 20 so it will convey the ejected sample into, andthrough, the column. Housing passage 21 is shown in simple T connectionto passage 20, flowing the carrier gas into passage 20.

The pressure of the carrier gas source is only slightly aboveatmospheric. Therefore, it is possible that the ejecting gas from source17 could push the sample from plug passage 4 so fast that its pressurewould cause a part of the sample to flow up housing passage 21 for afinite distance. This side-track of a portion of the sample interruptsthe smooth flow desired for the sample into the column, causing doubleindications of the same components.

To avoid this interruption in flow, the quantity of ejecting gas shouldbe fixed at a value which will cause all the sample to flow past housingpassage 21 smoothly, without interruption. A volume of ejecting gascould .be isolated between valves and released when plug passage 4 ispositioned as shown in FIG. 3. The result would be a smooth, continuous,uninterrupted flow of the sample into the column.

Preferred embodiment FIG. 4 represents a more simple and efficient wayto apply the sealing gas pressure to the sealing surface of a plugvalve. Valve 31 has a housing 32 similar to the structure of FIG. 1.Plug 33 has a passage 34 for the high pressure liquid sample. Thesealing surface 35 of plug 33 extends about the ends of passage 34,sealing against the walls of housing cavity 36.

Housing cavity 36 has a volume 36A on one side of plug sealing surface35 and volume 36B on the other side of the plug sealing surface. Source37 simultaneously develops pressure in housing volumes 36A and 363through passageway 38 in plug 33.

Passageway 38 extends from plug face 39 to plug face 39A and equalizesthe pressures of 36A and 36B. The passageway can be formed as shown. Apin from base 40 extending into the body of plug 33 is disclosed with anaxial bore to which a passage in the plastic body of plug 33 connects.However, specifically disclosed here, the concept is to have thispassageway 38 equalize the sealing pressure of source 37 at faces 39,39A, or in volumes 36A and 36B, placing the complete sealing surfaceabout sample passage 34 under the sealing pressure.

From the foregoing it will be seen that this invention is one welladapted to attain all of the ends and objects hereinabove set forth,together with other advantages which are obvious and which are inherentto the method and apparatus.

It will be understood that certain features and subcombinations are ofutility and may be employed without reference to other features andsubcombinations. This is contemplated by and is within the scope of theclaims.

As many possible embodiments may be made of the invention withoutdeparting from the scope thereof, it is to be understood that all matterherein set forth or shown in the accompanying drawings is to beinterpreted as illustrative and not in a limiting sense.

The present invention having been described, what is claimed is:

1. A system for injecting a sample of high pressure liquid to beanalyzed into a chromatographic column, including:

a valve housing having a cavity whose walls comprise a sealing surfacefor a valve plug,

a valve plug positioned in the housing cavity to bring its outer surfaceinto sealing engagement with the cavity walls,

a passage formed in the plug to extend to the sealing surfaces of thecavity and plug walls,

a first passage in the housing which is located to register with theplug passage in a first of the positions to which the plug is rotated,

a source of high pressure liquid sample communicated with the firstpassage to conduct a sample of the liquid into the plug passage when theplug is in the first of its positions,

a second passage in the housing which is located to register with theplug passage in a second of the positions to which the plug is rotated,

means for ejecting the sample from the plug passage into the secondhousing passage,

a source of carrier gas at a pressure substantially less than that ofthe sample connected to the second housing passage,

a chomatographic column connected to the second housing passage toreceive the sample and carrier gas for analysis of the sample, and

a third passage in the housing located to supply a fluid pressure atleast as great as that of the sample to the sealing engagement betweenthe outer surface of the plug and the cavity walls to prevent escape ofhigh pressure liquid from the plug passage before transfer of the sampleto the column.

2. The system of claim 1 having a passage system including the thirdhousing passage arranged to apply the fluid pressure to both sides ofthe valve plug in the housing cavity to balance the forces on the plugfrom the fluid pressure.

References Cited UNITED STATES PATENTS 3,267,736 8/1966 Boettger 73-4222,315,058 3/1943 Holt et al l37240 3,183,925 5/1965 Hoyle et al.137-24614 3,181,552 5/1965 Jackson 137-246.12 3,318,154 5/ 1967 Rendina73422 3,306,111 2/1967 Ferrin 73-23.1

RICHARD C. 'QUEISSER, Primary Examiner VICTOR J. TOTH, AssistantExaminer US. Cl. X.R. 73-422

